A wireless device may connect to a telecommunications network, and the wireless device may be assigned an Internet Protocol address. The telecommunications network may in turn provide connectivity to the Internet. Once connected to the telecommunications network, the wireless device may then communicate with other devices on the telecommunications network or on the Internet. The wireless device may communicate with a Session Initiation Protocol server, which can be used to establish sessions between the wireless device and a network device.
The wireless device may register with the Session Initiation Protocol server, such as by sending the Session Initiation Protocol server a register message that includes the current Internet Protocol address of the wireless device. The Session Initiation Protocol server may then start an expiration timer for the registration, which can be periodically reset by the wireless device. The registration can remain active as long as the timer does not expire. Once registered, the Session Initiation Protocol server may be used to establish sessions between the wireless device and other devices. For example, the Session Initiation Protocol Server may receive a request from the network device to establish a session between the network device and the wireless device. The Session Initiation Protocol server may forward the request directly to the wireless device. Alternatively, the Session initiation Protocol server may notify the network device of the wireless device's current address, and the network device can send the request directly to the wireless device.
The wireless device, however, may disconnect from the telecommunications network without deregistering from the Session Initiation Protocol server. For example, the wireless device may lose contact over its air interface with the telecommunications network. Although disconnected from the wireless telecommunications network, the Session Initiation Protocol server may still maintain the registration for the wireless device, because the wireless device did not deregister and the expiration timer has not yet expired.
Since the expiration timer remains active for a period of time after the wireless device disconnects from the telecommunications network, the Session Initiation Protocol server may still receive requests to establish a session with the wireless device, and it may attempt to forward those requests to the wireless device. It may also attempt to forward other messages to the disconnected wireless device, such as messages in an already established session. Additionally, the Session Initiation Protocol server may continue to inform other devices of the wireless device's current address, and the other devices may then attempt to send messages directly to the wireless device.
The processing performed by the Session Initiation Protocol server in attempting to send messages to the disconnected wireless device may delay processing messages destined for devices that are connected to the telecommunications network or to the Internet. Additionally, the messages sent to the disconnected wireless device may slow down other data traffic on the networks, and this can slow down communications between devices connected to the networks.
Therefore, there exists a need for an improved method for deregistering a wireless device from a Session Initiation Protocol server.